Climbing Stairs Problem in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to return the base case when n is 1 or 2.

DSA Typescript

function climbStairs(n: number): number {
  if (n <= 2) return [1];
  // rest of the code
}

Drag options to blanks, or click blank then click option'

An

B1

C2

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Returning 1 for all base cases

Returning 0 which means no ways

When n is 1 or 2, the number of ways to climb is n itself.

2fill in blank

medium

Complete the code to use recursion for climbing stairs.

DSA Typescript

function climbStairs(n: number): number {
  if (n <= 2) return n;
  return climbStairs(n - 1) [1] climbStairs(n - 2);
}

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A*

B-

C+

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition

Forgetting to return the sum

The total ways to climb n steps is the sum of ways to climb n-1 and n-2 steps.

3fill in blank

hard

Fix the error in the iterative solution to climb stairs.

DSA Typescript

function climbStairs(n: number): number {
  if (n <= 2) return n;
  let first = 1, second = 2;
  for (let i = 3; i <= n; i++) {
    let third = first [1] second;
    first = second;
    second = third;
  }
  return second;
}

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A+

B-

C*

D/

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition

Incorrect variable updates

Each step count is the sum of the previous two counts.

4fill in blank

hard

Fill both blanks to create a memoized recursive solution.

DSA Typescript

function climbStairs(n: number, memo: number[] = []): number {
  if (n <= 2) return n;
  if (memo[n] !== undefined) return memo[n];
  memo[n] = climbStairs(n [1], memo) [2] climbStairs(n - 2, memo);
  return memo[n];
}

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A- 1

B+ 1

C+

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using n + 1 instead of n - 1

Using subtraction instead of addition to combine results

We subtract 1 from n for the first recursive call and add the results of both calls.

5fill in blank

hard

Fill all three blanks to create a bottom-up dynamic programming solution.

DSA Typescript

function climbStairs(n: number): number {
  if (n <= 2) return n;
  const dp: number[] = [0, 1, 2];
  for (let i = 3; i <= n; i++) {
    dp[i] = dp[i [1]] [2] dp[i [3]];
  }
  return dp[n];
}

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A- 1

B+

C- 2

D*

Attempts:

3 left

💡 Hint

Common Mistakes

Using multiplication instead of addition

Incorrect indices for dp array

Each dp[i] is the sum of dp[i-1] and dp[i-2].